Date registered: Jul 2013
Vehicle: 1998 SL500
Location: Saint Augustine, FL
Mentioned: 7 Post(s)
Quoted: 348 Post(s)
If you have the Bose system almost any head unit will drive it, this quite contrary to conventional wisdom. The BE1492 and BE1692 stock radios drive the Bose amplfier via their loudspeaker outputs, which are rated at 15W or so. The low impedance speaker outputs are terminated in the Bose amp by some fairly high resistance, but not the usual 10k+ Ohms typically seen. This is why a 4 V or better output is needed if you try to drive the Bose amp from pre-amp outputs.
Driving the amp from loudspeaker outputs is not the best interface, however for automotive environments THD levels of 0.5 or even 1.0+% are pretty much indistinguishable from better performance. Also the Bose system manipulates frequency and phase response to such an extent that any other "speaker output" interface related issues become insignificant.
Add a crummy MP3 source to the mix and they become irrelevant...